Reuters reports, the enlargement of the sites follows an October 2022 deal in which Iran agreed to provide missiles to Russia, which has been seeking them for its war against Ukraine. Tehran also supplies missiles to Yemen's Houthi rebels and the Lebanese militia Hezbollah, both members of the Iran-backed Axis of Resistance against Israel.
Images taken by commercial satellite firm Planet Labs of the Modarres military base in March and the Khojir missile production complex in April show more than 30 new buildings at the two sites, both of which are located near Tehran.
According to Reuters, these images show many of the structures are surrounded by large dirt berms. Such earthworks are associated with missile production and are designed to stop a blast in one building from detonating highly combustible materials in nearby structures, said Jeffrey Lewis of the Middlebury Institute of International Studies at Monterey.
The expansions began at Khojir in August last year and at Modarres in October, Lewis said, based on images of the sites.
Iran's arsenal is already the largest in the Middle East, estimated at more than 3,000 missiles, including models designed to carry conventional and nuclear warheads, experts say.
Reuters claims that Modarres and Khojir sites are being expanded to boost production of conventional ballistic missiles.
Reuters claims that some of the new buildings would also allow a doubling of drone manufacturing. Drones and missile components would be sold to Russia, drones would be provided to the Houthis and missiles to Hezbollah.
Iran's mission to the United Nations did not respond to a Reuters request for comment on the expansion of the complexes. Tehran has previously denied providing drones and missiles to Russia and the Houthis.
Houthi spokesperson Mohammed Abdulsalam said a boost in Iran's weapons manufacturing would not have any impact in Yemen because the Houthis develop and manufacture aircraft independent of Iran.
Lewis analyzed the Planet Labs imagery with Decker Eveleth, an associate research analyst at CNA, a Washington think-tank, as part of a Middlebury project that monitors Iranian missile infrastructure.
The two US researchers said in separate interviews that it was not clear from the photos what kinds of missiles would be produced at the new facilities, which still appeared to be under construction.
Any increase in Tehran's missile or drone production would be concerning to the United States, which has said that Iranian drones help sustain Russia's assault on Ukrainian cities, and to Israel as it fends off attacks from Iran-backed groups, including Hezbollah.
Reuters in February reported that Iran had sent surface-to-surface ballistic missiles to Russia for use against Ukraine. Iran denied providing the weapons. Washington said it could not confirm the transfers but it assumed Tehran intended to provide missiles to Moscow.
On November 12, 2011, a massive explosion destroyed a large swath of Shadid Modarres associated with solid fuel missiles, killing 17 IRGC officers. They included Gen. Hassan Moqaddam, regarded by Iran as the "architect" of its ballistic missile program.
Construction at Shahid Modarres, which began again after the 2011 explosion, accelerated last year.
